title: Common mechanistic themes for the powerstroke of kinesin-14 motors.
abstract: Kar3Cik1 is a heterodimeric kinesin-14 from Saccharomyces cerevisiae involved in spindle formation during mitosis and karyogamy in mating cells. Kar3 represents a canonical kinesin motor domain that interacts with microtubules under the control of ATP-hydrolysis. In vivo, the localization and function of Kar3 is differentially regulated by its interacting stoichiometrically with either Cik1 or Vik1, two closely related motor homology domains that lack the nucleotide-binding site. Indeed, Vik1 structurally resembles the core of a kinesin head. Despite being closely related, Kar3Cik1 and Kar3Vik1 are each responsible for a distinct set of functions in vivo and also display different biochemical behavior in vitro. To determine a structural basis for their distinct functional abilities, we used cryo-electron microscopy and helical reconstruction to investigate the 3-D structure of Kar3Cik1 complexed to microtubules in various nucleotide states and compared our 3-D data of Kar3Cik1 with that of Kar3Vik1 and the homodimeric kinesin-14 Ncd from Drosophila melanogaster. Due to the lack of an X-ray crystal structure of the Cik1 motor homology domain, we predicted the structure of this Cik1 domain based on sequence similarity to its relatives Vik1, Kar3 and Ncd. By molecular docking into our 3-D maps, we produced a detailed near-atomic model of Kar3Cik1 complexed to microtubules in two distinct nucleotide states, a nucleotide-free state and an ATP-bound state. Our data show that despite their functional differences, heterodimeric Kar3Cik1 and Kar3Vik1 and homodimeric Ncd, all share striking structural similarities at distinct nucleotide states indicating a common mechanistic theme within the kinesin-14 family.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347, USA.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Gonzalez
authors.forename: Julia
authors.initials: J
authors.lastname: Cope
authors.forename: Katherine C
authors.initials: KC
authors.lastname: Rank
authors.forename: Chun Ju
authors.initials: CJ
authors.lastname: Chen
authors.forename: Peter
authors.initials: P
authors.lastname: Tittmann
authors.forename: Ivan
authors.initials: I
authors.lastname: Rayment
authors.forename: Susan P
authors.initials: SP
authors.lastname: Gilbert
authors.forename: Andreas
authors.initials: A
authors.lastname: Hoenger
mesh_terms: D000266:Adenylyl Imidodiphosphate / Q000737:chemistry; D020285:Cryoelectron Microscopy; D008868:Microtubule Proteins / Q000737:chemistry / Q000648:ultrastructure*; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000648:ultrastructure*; D008870:Microtubules / Q000737:chemistry / Q000648:ultrastructure*; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000648:ultrastructure*
chemical_list: C076025:CIK1 protein, S cerevisiae; C063504:KAR3 protein, S cerevisiae; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins; D000266:Adenylyl Imidodiphosphate
keywords: Cryo-electron microscopy; Helical 3-D analysis; Kar3Cik1; Kinesin-14; Microtubules; Molecular docking